mirror of https://github.com/apache/druid.git
170 lines
5.3 KiB
Markdown
170 lines
5.3 KiB
Markdown
---
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layout: doc_page
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---
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# Select Queries
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Select queries return raw Druid rows and support pagination.
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```json
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{
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"queryType": "select",
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"dataSource": "wikipedia",
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"dimensions":[],
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"metrics":[],
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"granularity": "all",
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"intervals": [
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"2013-01-01/2013-01-02"
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],
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"pagingSpec":{"pagingIdentifiers": {}, "threshold":5}
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}
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```
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There are several main parts to a select query:
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|property|description|required?|
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|--------|-----------|---------|
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|queryType|This String should always be "select"; this is the first thing Druid looks at to figure out how to interpret the query|yes|
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|dataSource|A String defining the data source to query, very similar to a table in a relational database|yes|
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|intervals|A JSON Object representing ISO-8601 Intervals. This defines the time ranges to run the query over.|yes|
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|filter|See [Filters](Filters.html)|no|
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|dimensions|The list of dimensions to select. If left empty, all dimensions are returned.|no|
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|metrics|The list of metrics to select. If left empty, all metrics are returned.|no|
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|pagingSpec|A JSON object indicating offsets into different scanned segments. Query results will return a `pagingIdentifiers` value that can be reused in the next query for pagination.|yes|
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|context|An additional JSON Object which can be used to specify certain flags.|no|
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The format of the result is:
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```json
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[{
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"timestamp" : "2013-01-01T00:00:00.000Z",
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"result" : {
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"pagingIdentifiers" : {
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"wikipedia_2012-12-29T00:00:00.000Z_2013-01-10T08:00:00.000Z_2013-01-10T08:13:47.830Z_v9" : 4
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},
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"events" : [ {
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"segmentId" : "wikipedia_editstream_2012-12-29T00:00:00.000Z_2013-01-10T08:00:00.000Z_2013-01-10T08:13:47.830Z_v9",
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"offset" : 0,
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"event" : {
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"timestamp" : "2013-01-01T00:00:00.000Z",
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"robot" : "1",
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"namespace" : "article",
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"anonymous" : "0",
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"unpatrolled" : "0",
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"page" : "11._korpus_(NOVJ)",
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"language" : "sl",
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"newpage" : "0",
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"user" : "EmausBot",
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"count" : 1.0,
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"added" : 39.0,
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"delta" : 39.0,
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"variation" : 39.0,
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"deleted" : 0.0
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}
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}, {
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"segmentId" : "wikipedia_2012-12-29T00:00:00.000Z_2013-01-10T08:00:00.000Z_2013-01-10T08:13:47.830Z_v9",
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"offset" : 1,
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"event" : {
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"timestamp" : "2013-01-01T00:00:00.000Z",
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"robot" : "0",
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"namespace" : "article",
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"anonymous" : "0",
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"unpatrolled" : "0",
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"page" : "112_U.S._580",
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"language" : "en",
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"newpage" : "1",
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"user" : "MZMcBride",
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"count" : 1.0,
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"added" : 70.0,
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"delta" : 70.0,
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"variation" : 70.0,
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"deleted" : 0.0
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}
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}, {
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"segmentId" : "wikipedia_2012-12-29T00:00:00.000Z_2013-01-10T08:00:00.000Z_2013-01-10T08:13:47.830Z_v9",
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"offset" : 2,
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"event" : {
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"timestamp" : "2013-01-01T00:00:00.000Z",
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"robot" : "0",
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"namespace" : "article",
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"anonymous" : "0",
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"unpatrolled" : "0",
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"page" : "113_U.S._243",
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"language" : "en",
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"newpage" : "1",
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"user" : "MZMcBride",
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"count" : 1.0,
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"added" : 77.0,
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"delta" : 77.0,
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"variation" : 77.0,
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"deleted" : 0.0
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}
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}, {
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"segmentId" : "wikipedia_2012-12-29T00:00:00.000Z_2013-01-10T08:00:00.000Z_2013-01-10T08:13:47.830Z_v9",
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"offset" : 3,
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"event" : {
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"timestamp" : "2013-01-01T00:00:00.000Z",
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"robot" : "0",
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"namespace" : "article",
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"anonymous" : "0",
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"unpatrolled" : "0",
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"page" : "113_U.S._73",
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"language" : "en",
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"newpage" : "1",
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"user" : "MZMcBride",
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"count" : 1.0,
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"added" : 70.0,
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"delta" : 70.0,
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"variation" : 70.0,
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"deleted" : 0.0
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}
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}, {
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"segmentId" : "wikipedia_2012-12-29T00:00:00.000Z_2013-01-10T08:00:00.000Z_2013-01-10T08:13:47.830Z_v9",
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"offset" : 4,
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"event" : {
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"timestamp" : "2013-01-01T00:00:00.000Z",
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"robot" : "0",
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"namespace" : "article",
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"anonymous" : "0",
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"unpatrolled" : "0",
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"page" : "113_U.S._756",
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"language" : "en",
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"newpage" : "1",
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"user" : "MZMcBride",
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"count" : 1.0,
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"added" : 68.0,
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"delta" : 68.0,
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"variation" : 68.0,
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"deleted" : 0.0
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}
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} ]
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}
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} ]
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```
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The `threshold` determines how many hits are returned, with each hit indexed by an offset.
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The results above include:
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```json
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"pagingIdentifiers" : {
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"wikipedia_2012-12-29T00:00:00.000Z_2013-01-10T08:00:00.000Z_2013-01-10T08:13:47.830Z_v9" : 4
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},
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```
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This can be used with the next query's pagingSpec:
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```json
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{
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"queryType": "select",
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"dataSource": "wikipedia",
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"dimensions":[],
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"metrics":[],
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"granularity": "all",
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"intervals": [
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"2013-01-01/2013-01-02"
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],
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"pagingSpec":{"pagingIdentifiers": {"wikipedia_2012-12-29T00:00:00.000Z_2013-01-10T08:00:00.000Z_2013-01-10T08:13:47.830Z_v9" : 5}, "threshold":5}
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}
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Note that in the second query, an offset is specified and that it is 1 greater than the largest offset found in the initial results. To return the next "page", this offset must be incremented by 1 with each new query. When an empty results set is recieved, the very last page has been returned.
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